Press brake with hydraulic ram adjustment

ABSTRACT

A PRESS BRAKE FOR BENDING METAL. A HYDRAULIC CYLINDER AND PISTON ARRANGEMENT IS FIXED AT ITS UPPER END TO THE DRIVE MEANS AND IS FIXED AT ITS MOVING END TO THE RAM. A HYDRAULIC PUMP IS CONNECTED TO THE HYDRAULIC DRIVE CYLINDER TO ADJUST THE SPACING BETWEEN THE UPPER AND MOVING ENDS OF THE CYLINDER AND PISTON ARRANGEMENT SO THAT THE SPACING BETWEEN THE RAM AND THE BED IS ADJUSTED TO THE DESIRED AMOUNT. MEANS ARE PROVIDED TO LOCK THE HYDRAULIC FLUID IN PLACE ON EACH SIDE OF THE PISTON IN THE HYDRAULIC CYLINDER SO THAT THE RAM REMAINS LOCKED AT THE FIXED SPACING. RELIEF MEANS ARE INTERCONNECTED TO THE HYDRAULIC FLUID ON THE HIGH PRESSURE SIDE OF THE PISTON FOR RELIEVING THE FLUID PRESSURE AT A PRESELECTED LEVEL TO AVOID DAMAGE TO THE PRESS BRAKE.

Jan. 5, 1971 K. J. HANDLER 3,

' PRESS BRAKE WITH HYDRAULIC RAM ADJUSTMENT Filed Nov. 20,1968 2 Sheets-Sheet l dlenrze/fi afc'l andler Jan. 5, 1971 K. J. HANDLER 3,552,182

PRESS BRAKE WITH HYDRAULIC RAM ADJUSTMENT Filed Nov. 20, 1968 2 Sheets-Sheet 2 J16 118 j; 1/2 X VI/l/ I V Z Z a 5 i a g I 4 1 E A. 3.? w i 1 United States Patent 0 3,552,182 PRESS BRAKE WITH HYDRAULIC RAM ADJUSTMENT Kenneth J. Handler, Wilmette, Ill., assignor to Wisconsin Machine Corporation, a corporation of Illinois Filed Nov. 20, 1968, Ser. No. 777,346 Int. Cl. B21d 55/00 US. Cl. 72432 3 Claims ABSTRACT OF THE DISCLOSURE cylinder so that the ram remains locked at the fixed spacing. Relief means are interconnected to the hydraulic fluid on the high pressureside of the piston for relieving the fluid pressure at a preselected level to avoid damage to the press brake.

BACKGROUND OF THE INVENTION Field of the invention and description of the prior art This invention relates to a press brake and it particularly relates to a press brake having hydraulic drive means for adjusting the relative spacing between the bed and the ram of the machine.

Press brakes used for bending sheet metal, bars, or the like generally comprise a bed on which the material to be bent is placed and a movable ram which is aligned above the bed and moves down with force against the metal part to effect the desired bending. These press brakes are capable of bending material having varying thicknesses. It has been the general practice in the art to adjust the spacing between the ram and the bed by mechanical means, such as a screw or jack arrangement. An operator manually adjusts the jack or screw setting so as to change the relative distance between the bed and the ram, the jack moving the ram up or down relative to the bed. These manual adjustments'are time consuming and relatively inaccurate. A further difficulty is encountered with these jack arrangements when the press brake be- F comes ammed because of an overlooked. These ack arrangements are difficult to release. Also, a jam may result in serious damage to the drive mechanism as well as to the jack arrangement.

Significant improvements have been made over apparatus which use mechanical jacks in the provision of hydraulic cylinder and piston arrangements for adjusting the spacing between the bed and the ram. These arrangements, wherein hydraulic cylinders are used, provide significant improvements because the ram height adjustments may be made considerably faster and there is greater accuracy in making the setting. Also, the hydraulic system enables a jam to be released rapidly because the operator merely needs to open manual shut off valves to release the hydraulic fluid locked in the pressure system. The ram retreats automatically, and the machine is returned to service within a matter of minutes.

Another advantage in the use of hydraulic cylinders for adjusting the ram height would appear to be that the hydraulic fittings and hoses should rupture before any serious and expensive damage could occur to the press brake, such as to the frame or the drive of the machine. It has been found, however, that hoses and fittings of hydraulic pressure systems rupture at highly varying pressures. Hydraulic fittings and hoses are guaranteed to rupture above a certain value, but the actual rupture pressure may extend over a wide range above the guaranteed value. As a result, the machine would ultimately be damaged by an overload when the hydraulic fittings or hoses rupture at a pressure higher than desired, so that rather than simply losing oil through a hose rupture, serious mechanical damage can result to the press brake.

It is therefore an object of this invention to provide an improved press brake using a hydraulic ram height adjustment arrangement wherein the hydraulic fluid is relieved before there can be any damage done to the operating parts of the machine.

It is also an object of this invention to provide an im- SUMMARY OF THE INVENTION proved press brake wherein the apparatus includes a hydraulic system for adjusting the ram height, which hydraulic system includes a rupture disc which relieves the over pressure of the hydraulic system at a predetermined value and before any damage can be done to the machine.

Further purposes and objects of this invention will appear as the specification proceeds.

All of the foregoing objects are accomplished by providing a press brake which comprises a frame, a stationary bed on the frame for receiving material to be bent thereon, a ram on the frame which is aligned above the bed, means for driving the ram toward the bed to bend the material interposed between the bed and the ram, hydraulic cylinder and piston means having first and second end portions, the first end portion being connected to the drive means, the second end portion being connected to the ram, means connected to the hydraulic cylinder and piston means to adjust the spacing between the end portions by the use of hydraulic fluid so that the spacing between the ram and the bed is adjusted to a desired spacing, means to normally lock the hydraulic fluid within the cylinder and piston means during use so that the ram remains locked at a fixed spacing from the bed, and means interconnected to the hydraulic fluid in the cylinder and piston means to relieve the pressure of the fluid when it reaches a preselected level so as to avoid damage to the press brake.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a press brake using my improved hydraulic system for adjusting the ram height;

FIG. 2 is a schematic drawing of the hydraulic ram height adjustment circuitry used in the press brake of FIG. 1.

FIG. 3 is a perspective view of a height adjustment cylinder mounted on a drive gear and eccentric ararngement which drives the cylinder and the ram downwardly; and

FIG. 4 is an enlarged cross-sectional view of the hydraulic cylinder and piston arrangement having a burst plug therein for relieving the pressure of the pressurized hydraulic fluid at a predetermined level.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1, a press brake, generally 10, includes a base 12, upright sides 14, and an overhead assembly 16. An operating foot pedal 18 is operatively connected to the brake 10 at its lower end. The pedal 18 operates a clutch (not shown) contained within a housing 20 through an operating linkage, generally 22. The linkage 22 includes several members which are secured to one of the upright sides 14. The overhead assembly 16, contains a drive mechanism (not shown) which operates the press brake 10.

The press brake includes a die holder 24 upon which a female die 26 is mounted. The elongated die holder 24 has a ram 28 movably aligned thereabove. The ram 28 generally constitutes a heavy metal plate having a male die 30 fixedy secured at its lower end and in alignment directly above the female die 26. The sheet material or bar stock which is to be bent is inserted between the fixed die 26 and the moving die 30. The ram 28 is then driven downwardly to cause the desired bending of the material.

Since the operating performance of the press brake 10 is dependent upon material thickness, the die configuration, the amount of bending desired, and the force applied during the bending operation, to accomplish the desired results, it is necessary to adjust the spacing between the dies 26 and 30. In order to adjust the spacing between the dies 26 and 30, a pair of laterally spaced hydraulic cylinder members 32 are secured, at their lower ends, to the upper end of the ram 28, as best shown in FIG. 1.

In FIG. 3, one of the hydraulic cylinders 32 is shown connected at its upper end to a drive gear 34. The drive gear 34 is operatively connected to drive means (not shown) for operating the ram 28. The gear 34 has an integral shaft portion 35 which is eccentrically and rotatably mounted on a fixed pivot 36. The cylinder upper housing 38 is rotatably mounted on the shaft 35. As the gear 34 and shaft 35 are rotated about the fixed pivot 36, the entire hydraulic cylinder is moved downwardly by the cranking action of the eccentrically movable shaft 35.

A piston rod 40 extending outwardly from the hydraulic cylinder 32 is fixedly connected to mounting member 42. The mounting member 42 includes a ball and socket joint for pivotally connecting the piston rod 40 to the ram 28. The ram 28 moves in a vertical plane. The ball and socket pivot connection between the mounting member 42 and the ram 28 permits the vertically moving ram 28 to be driven downward by the eccentrically moving cylinder 32.

Referring to FIGS. 2 and 3 the hydraulic system for the hydraulic cylinder 32 is shown. The hydraulic system constitutes two completely separate systems on each side of piston 88 contained within each hydraulic cylinder 32. The system on the upper side of the piston 88 is the side which undergoes the high pressure during the operation of the ram 28. The system of the lower side of the piston is ordinarily subjected to relatively low pressures which are required to raise and support the weight of the ram 28.

The upper system includes a reservoir or tank 44. The

oil in the tank is under constant air pressure which passes through an inlet 45, a filter 46, a regulator 47, and then into the tank 44. The air pressure assures a non-turbulent flow of oil from the tank to assure against ingestion of air into the hydraulic fluid, which would create an objectionable condition because of the compressibility of air.

The hydraulic fluid passes through a strainer 48 in an outlet line 49. The line 49 branches into two lines 50 which are each connected into the upper side of the piston 88 in the housing 38. A high pressure shut off valve 51 is interconnected in each of the branch lines 50.

The lower system includes a hydraulic fluid storage tank 52, normally maintained under atmospheric pressure. The oil is withdrawn from the tank 52 through an outlet line 53 and through a strainer 54 by a pump 55. A reversible electric motor 56 drives the pump 55. A solenoid valve 57 is on the pressure side of the pump and is open when the motor is running and is closed when the motor is off. The outlet line 53 branches to a pressure line 58 and a line 59 which leads to a hydraulic accumulator 60. The pressure line 58, in turn, branches into two cylinder inlet lines 61 which pass to the lower side of the piston 88.

Referring to FIG. 4, the cylinder 32 includes the housing 38 which is secured to the drive shaft 36. An inlet 76 for the pressurized hydraulic fluid from the line 50 is provided in the pressure end of the cylinder 32. The hydraulic cylinder 32 also has an end closure member 82 and a cylindrical outer wall 84 which is positioned between the housing 38 and the closure member 82. An inlet 83 from the line 61 is provided in the closure member 82 for communication of the fluid with the cylinder 32. Tie rods, shown in FIG. 3, are provided for firmly securing the closure member 82 and the cylinder wall 84 to the housing 38. Pressure seals 86 are provided between the inner surface of the cylinder wall 84 and the recessed outer wall of the end member 82 and between the cylinder wall and the recessed outer wall of the housing 38. The seals 86 are high pressure seals and prevent undesired leakage of the pressurized hydraulic fluid.

The piston 88 is slidably positioned within the cylinder walls 84 and reciprocates between the end member 82 and the housing 38. The piston 88 is secured to a piston rod 90. A central aperture in the piston 88 receives the restricted end of the piston rod 90. A hydraulic seal 92 is carried between the piston rod and the walls defining the aperture of the piston 88, in order to prevent passage of hydraulic fluid from one side of the piston to the other side. A nut threadably engages the end of the piston rod 90 and secures the piston 88 in place against the enlarged portion of the piston rod 90.

The outer cylindrical periphery of the piston 88 in cludes a pair of U-cup packings 94 in its opposite ends and a packing 96 is interposed therebetween. The U-cups 94 are held in place by means of retaining rings 98 received in the outer periphery of the piston 88. The U-cups 94 and the packing 96 are in sliding contact with the face of the cylindrical walls 84 of the cylinder 32 and prevent the passage of the pressurized hydraulic fluid from the high pressure side of the piston to the low pressure side of the piston. These packings are important in the structure because any passage of pressurized hydraulic fluid from one side of the piston to the other will adversely affect the vertical adjustment of the ram 28. The hydraulic fluid is therefore locked in place after the setting of the vertical adjustment of the ram has been accomplished. The lock valves 72, the accumulator 60, and the packings between the high pressure side and the low pressure side of the piston all cooperate to assure that there will be no loss of pressurized hydraulic fluid to adversely affect the stability of the ram adjustment.

The piston rod 90 passes through an aperture provided in the closure member 82. A U-cup 100 and rod bearing 102, permit sliding engagement between the piston rod 90 and the closure member 82 while at the same time the leakage of the hydraulic fluid from between the end plate and the piston rod is prevented. The packing 100 and rod bearing 102 are secured in place by an annular plate 104 which is held to the end plate 82 by bolts. The outer moving end 106 of the piston rod 90 is threaded and receives the ram mounting 42 which includes the ball and socket joint for pivotal connection to the ram.

In the described invention, it is important that the apparatus 10 is to be protected from damage which might be caused from overloading the apparatus. For this purpose, a relief channel 108 extends into the pressure chamber 78 through the cylinder housing 38. The relief opening 108 is closed at its outer end by a burst plug 110. The burst plug is threadably and sealably received by the relief port 108 and acts to prevent the leakage of any liquid therethrough. The plug 110 includes a housing portion 112 having a central aperture 114 therein. The central aperture is enclosed by a metallic rupture disc 116. The rupture disc 116 is secured in place by a securing member 118 which is received in the outer end of the housing 112. The securing member 118 firmly holds the disc 116 in place. The disc 116 is designed to relieve the pressure in the chamber 78 at a preselected pressure, such as 3200 pounds per square inch, so as to prevent damage to the apparatus by an overload.

If an overload occurs, the disc 116 will burst and the hydraulic fluid pressure will be relieved and the machine will be temporarily disabled. This will prevent any damage to the apparatus. By the use of the burst plug 110, there is assurance that there will be no damage to the apparatus in case of a jam or an overload. The only expense involves replacing the used rupture plug 110. The provision of this burst plug 110 is a simple and inexpensive way to avoid serious damage, and tlsus provides a very important addition to the overall performance of the apparatus.

In the operation of the press brake 10, when the operator desires to adjust the spacing between the fixed and moving dies 26 and 30, he presses a down button (not shown) which opens the valve 57, operates motor 56, and the weight of the ram forces the pistons 88 in each cylinder 32 downwardly. The fluid, in efiect, is pushed out of the cylinder 32, and passes through the pump 55 and up into the hydraulic fluid storage tank 52. The fluid on the upper side of the piston fills the space on the upper side of the piston 88. Air pressure on the oil in the tank 44 assures non-turbulent flow to avoid air entering the fluid. The ram moves to the dead center down position where the dies 26 and 30 are in intimate contact. The valves 51 are then closed to confine the incompressible fluid in a defined space above the piston 88. The operator then charges the lower side of the piston 88 by operating the motor 56 to drive the pump 55, while the valve 57 is also opened. This charges the accumulator 60 to a pressure of for example, 425 p.s.i., as limited by a relief valve in the pump. Since the valves 51 are closed during operation of the pump 55, the ram does not move upwardly. The valve 57 closes and the motor is stopped. The valves 51 are cracked and the pressure developed on the lower side of the pistons 88 raises the pistons 88, and thereby the ram, the desired amount. The valves 51 are then closed. The ram is thus locked at the desired height because each piston is locked between the two independent hydraulic systems.

The workpiece is then placed between the dies 26 and 30 and the operator steps on the pedal to activate the drive means. The drive means rotate drive gears 34 which, through the eccentric mounting, drives the ram 88 downwardly. If a jam should occur, at a pressure which does not burst the disc 116, the operator simply opens the valves 51 to permit the pressure to be relieved on the high pressure side of the piston 88. The pistons 88 are driven in a reverse or upward direction by the pressurized hydraulic fluid stored in the accumulator on the lower side of the piston. This automatically drives the ram upwardly and away from the bed 24. It is then simple to relieve the jam such as by removing the workpiece.

If an overload occurs which could damage the machine, the increased pressure in the pressure system and within the pressure chamber 78 of the hydraulic cylinder 32 will cause the rupture disc 116 of the plug 110 to burst. This relieves the pressure of the fluid on the pressure side of the cylinder. When the problem which caused the overload has been alleviated, the operator merely places a new rupture plug 110 into the relief aperture 108 and the apparatus is ready for further use.

While in the foregoing there has been provided a detailed description of a particular embodiment of the present invention, it is to he understood that all equivalents obvious to those having skill in the art are to be included Within the scope of the invention as claimed.

What I claim and desire to secure by Letters Patent is:

1. A press brake for bending material, said press brake comprising, in combination, a frame, a stationary bed on said frame for receiving said material thereon, a ram on said frame in alignment with and above said bed, means for driving said ram towards said bed to bend the material interposed between said bed and said ram, hydraulic cylinder and piston means having first and second end portions, said piston means having a high pressure side and a low pressure side, said first end portion being connected to said drive means, said second end portion being connected to said ram, hydraulic means connected to said hydraulic cylinder means for adjusting the spacing between said end portions and thereby the spacing between said ram and said bed, means to confine pressurized hydraulic fluid in the high pressure and low pressure sides of said piston means so that said ram is locked at a fixed spacing from said bed, and means interconnected into said high pressure side for relieving the pressure of said fluid when the fluid pressure exceeds a preselected level.

2. The apparatus of claim 1 wherein said first end portion of said hydraulic cylinder means is fixed and comprises the upper end of said cylinder and said second end portion of said hydraulic cylinder and piston means is movable and comprises a lower end of said piston means.

3. The apparatus of claim 1 wherein said relieving means comprises a plug member having a rupture disc which bursts at the said preselected pressure level.

References Cited UNITED STATES PATENTS 486,772 11/1892 Evans 72-453 2,128,152 8/1938 MacMillin 72--453 2,236,154 3/1941 Patrick 53 2,936,055 5/1960 Kassnel 72-43'2 3,426,873 2/1969 Tezuka 10053 3,481,171 12/1969 Alexandria 72432 3,487,772 1/1970 Kraft 10053 FOREIGN PATENTS 397,146 8/1933 Great Britain 72-432 CHARLES W. LANHAM, Primary Examiner G. P. CROSBY, Assistant Examiner 

